The present invention relates to liquid ink printers such as ink jet printers, and more particularly to such a printer including a non-scorching dryer for drying sheets carrying liquid ink images that are still wet without scorching such sheets even when such sheets are stalled in the such dryer. Printing in ink jet printers demands that excess moisture (generally water) on the surface of printed sheets be removed within a set time period and before the sheets are stacked. If the sheets are stacked before the images are dry, image smearing and offset occur. Devices that actively remove moisture, specifically water, from the sheet surface are referred to as dryers. A commonly used dryer is a hot air convective mass transfer drying system. While dryers are effective in rapidly removing the excess moisture from the sheets, dryers greatly increase printer power requirements and size. If dryers were used in small printers, the size and cost of these printers would greatly increase. Also, most small printers do not have the power capacity to accommodate an active dyer.
U.S. Pat. No. 4,970,528 to Beaufort et al. discloses an ink jet printing apparatus having a uniform heat flux dryer system which uses an infrared bulb and reflectors to transmit heat to the printed paper during the ink drying process. The freshly printed sheet is dried as it is fed from the printing apparatus along a 180.degree arc which surrounds the infrared bulb and reflectors.
U.S. Pat. No. 2,306,607 to Horton discloses a web drying device for sheets printed by an intaglio printing apparatus. The web drying device feeds the web along a series of rollers while exposing the web to heat blown onto the web by an exhaust fan. The prior art references all teach the use of some type of active heating element to dry the freshly printed sheets. As discussed above, these active dryers demand increased printer power capacity and also increase the size and cost of the printing apparatus which is unacceptable for a small, relatively inexpensive printer.
Thermal ink jet printing systems that require an ink drying system can benefit from the use of an infra red dryer due to its fast warm up time and fast energy transfer rate. However, unless the power density that the media is exposed to is very low (less than 0.8 watts/cm), scorching as evidenced by darkening, deformation, and odor, can occur if the media is exposed to the IR energy for longer the designed time such as during an undetected paper jam.